Jeh Johnson, who served as homeland security secretary in the Obama administration, said a proposal reportedly being considered by the White House to divert billions of dollars in disaster aid to fund the construction of a wall along the U.S.-Mexico border is "more legally plausible" than an earlier plan to use military funds.

"In my view, that's probably slightly more legally plausible. The earlier Defense [Department] authority was really trying to jam a square peg in round hole," Johnson said on "Face the Nation" Sunday. "This one is slightly more plausible, but politically highly objectionable because you're taking billions of dollars away from important civil work projects to recover from the hurricanes and the wildfires."

The White House, facing stiff resistance from Democrats in negotiations to reopen the government, directed the U.S. Army Corps of Engineers to explore using $13.9 billion in funds the corps received for disaster relief in 2018 to begin building a border wall, according to a congressional aide familiar with the matter. The money was earmarked for relief measures for Puerto Rico, California, Florida, Texas and other states hit by natural disasters in recent years.

"It appears this president is willing to even consider something as unconscionable as building a vanity wall with billions of dollars by taking it away from the life and safety of American citizens around the country," Democratic Rep. Tony Cárdenas of California told CBS News in Puerto Rico, where a congressional delegation is meeting with local officials and hosting fundraising events.

Johnson said it is ultimately up to congressional leaders to broker an agreement and reopen the government, which has been closed for 23 days, the longest shutdown in U.S. history.

He added the real "security crisis" near the southwestern border is the fact that thousands of DHS employees — including Coast Guard units, Border Patrol officers and Transportation Security Administration (TSA) personnel — are not being paid because of the prolonged partial government shutdown. Johnson said these federal workers are being inflicted with "all of sorts of stress and anxiety in their personal life about whether they are going to be paid and when. That's the real security crisis that I see."

Johnson said a more effective strategy to address the surge of Central American families heading toward the southwestern border — which he labeled a "humanitarian crisis" — is for the U.S. government to make a "long-term political commitment" to investing in the violence-torn and poverty-ridden Northern Triangle, comprising Guatemala, El Salvador and Honduras.

"The way to deal with this problem is frankly to make a long-term investment in helping to eradicate the poverty and violence in these three countries that are probably the most violent on earth," he said.

Asked about the fate of the Deferred Action for Childhood Arrivals (DACA) program, which he oversaw during Obama's tenure, Johnson said he did not want to make a prediction on how a conservative-leaning Supreme Court would rule in a lawsuit by several Republican attorneys general who argue the initiative, which shields approximately 800,000 young undocumented immigrants from deportation, is unconstitutional.